Eastern Equine Encephalitis (EEE) has been confirmed in the United Counties of Leeds and Grenville, Ontario. On September 15, 2024, a pony mare started showing acute neurologic signs (circling, head pressing, falling against the fence, stumbling, weakness, hypermetria). She was administered supportive treatment but was euthanized two days later as her clinical signs worsened. EEE was confirmed on October 2. The horse was not vaccinated against EEE. This is the 20th case of equine EEE in Ontario this year.